Author: Xue Feng ZhangPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Separation and Transition Control on Ultra-high-lift Low Pressure Turbine Blades in Unsteady Flow
Author: Xue Feng ZhangOn the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions
Author: On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781721575466
Category :
Languages : en
Pages : 36
Book Description
The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flowconditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding t
Axial Turbine Aerodynamics for Aero-engines
Author: Zhengping ZouPublisher: Springer
ISBN: 9811057508
Category : Technology & Engineering
Languages : en
Pages : 572
Book Description
This book is a monograph on aerodynamics of aero-engine gas turbines focusing on the new progresses on flow mechanism and design methods in the recent 20 years. Starting with basic principles in aerodynamics and thermodynamics, this book systematically expounds the recent research on mechanisms of flows in axial gas turbines, including high pressure and low pressure turbines, inter-turbine ducts and turbine rear frame ducts, and introduces the classical and innovative numerical evaluation methods in different dimensions. This book also summarizes the latest research achievements in the field of gas turbine aerodynamic design and flow control, and the multidisciplinary conjugate problems involved with gas turbines. This book should be helpful for scientific and technical staffs, college teachers, graduate students, and senior college students, who are involved in research and design of gas turbines.
On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions
Author: Meinhard SchobeiriNew Results in Numerical and Experimental Fluid Mechanics VII
Author: Andreas DillmannPublisher: Springer Science & Business Media
ISBN: 3642142435
Category : Technology & Engineering
Languages : en
Pages : 629
Book Description
th This volume contains the papers presented at the 16 DGLR/STAB-Symposium held at the Eurogress Aachen and organized by RWTH Aachen University, Germany, November, 3 - 4, 2008. STAB is the German Aerospace Aerodynamics Association, founded towards the end of the 1970's, whereas DGLR is the German Society for Aeronautics and Astronautics (Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal Oberth e.V.). The mission of STAB is to foster development and acceptance of the discipline “Aerodynamics” in Germany. One of its general guidelines is to concentrate resources and know-how in the involved institutions and to avoid duplication in research work as much as possible. Nowadays, this is more necessary than ever. The experience made in the past makes it easier now, to obtain new knowledge for solving today's and tomorrow's problems. STAB unites German scientists and engineers from universities, research-establishments and industry doing research and project work in numerical and experimental fluid mechanics and aerodynamics for aerospace and other applications. This has always been the basis of numerous common research activities sponsored by different funding agencies. Since 1986 the symposium has taken place at different locations in Germany every two years. In between STAB workshops regularly take place at the DLR in Göttingen.
An Experimental Investigation of Heat Transfer, Transition and Separation on Turbine Blades at Low Reynolds Number and High Turbulence Intensity
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 20
Book Description
The effects of turbulence intensity on the heat transfer distribution, transition and flow separation on a turbine blade was investigated at low Reynolds numbers. Measurements were performed in linear cascades (at both UCDavis and the USAF Academy) at low Reynolds number (67,000 to 144,000) representative of low pressure turbine stages at high altitude. Nominal turbulence intensities of 1% and 10% (generated with biplane lattice grids) were used. The heat transfer was measured with the uniform heat flux (UHF) or heated-coating method. The heated-coating was a gold-film and liquid crystals were used for the surface temperature measurement. A novel laser-tuft surface flow visualization method was also used. For low turbulence levels (1%) the pressure side of the blade exhibited streaks of varying heat transfer possibly associated with Taylor-Gortler vortices. With grid turbulence (10%) these streaks disappeared on the pressure side and the heat transfer nearly doubled. Gird turbulence also increased the heat transfer on the leading edge and suction surface, while advancing the location of boundary layer transition. Good agreement was generally found between the UCDavis and USAFA data. These cascade results compare favorably to those that have been reported with rotation.
Unsteady Computational Fluid Dynamics in Aeronautics
Author: P.G. TuckerPublisher: Springer Science & Business Media
ISBN: 9400770499
Category : Technology & Engineering
Languages : en
Pages : 432
Book Description
The field of Large Eddy Simulation (LES) and hybrids is a vibrant research area. This book runs through all the potential unsteady modelling fidelity ranges, from low-order to LES. The latter is probably the highest fidelity for practical aerospace systems modelling. Cutting edge new frontiers are defined. One example of a pressing environmental concern is noise. For the accurate prediction of this, unsteady modelling is needed. Hence computational aeroacoustics is explored. It is also emerging that there is a critical need for coupled simulations. Hence, this area is also considered and the tensions of utilizing such simulations with the already expensive LES. This work has relevance to the general field of CFD and LES and to a wide variety of non-aerospace aerodynamic systems (e.g. cars, submarines, ships, electronics, buildings). Topics treated include unsteady flow techniques; LES and hybrids; general numerical methods; computational aeroacoustics; computational aeroelasticity; coupled simulations and turbulence and its modelling (LES, RANS, transition, VLES, URANS). The volume concludes by pointing forward to future horizons and in particular the industrial use of LES. The writing style is accessible and useful to both academics and industrial practitioners. From the reviews: "Tucker's volume provides a very welcome, concise discussion of current capabilities for simulating and modellng unsteady aerodynamic flows. It covers the various pos sible numerical techniques in good, clear detail and presents a very wide range of practical applications; beautifully illustrated in many cases. This book thus provides a valuable text for practicing engineers, a rich source of background information for students and those new to this area of Research & Development, and an excellent state-of-the-art review for others. A great achievement." Mark Savill FHEA, FRAeS, C.Eng, Professor of Computational Aerodynamics Design & Head of Power & Propulsion Sciences, Department of Power & Propulsion, School of Engineering, Cranfield University, Bedfordshire, U.K. "This is a very useful book with a wide coverage of many aspects in unsteady aerodynamics method development and applications for internal and external flows." L. He, Rolls-Royce/RAEng Chair of Computational Aerothermal Engineering, Oxford University, U.K. "This comprehensive book ranges from classical concepts in both numerical methods and turbulence modelling approaches for the beginner to latest state-of-the-art for the advanced practitioner and constitutes an extremely valuable contribution to the specific Computational Fluid Dynamics literature in Aeronautics. Student and expert alike will benefit greatly by reading it from cover to cover." Sébastien Deck, Onera, Meudon, France
Separation Flow Control with Vortex Generator Jets Employed in an Aft-loaded Low-pressure Turbine Cascade with Simulated Upstream Wakes
Author: Kyle Adler GompertzPublisher:
ISBN:
Category : Turbines
Languages : en
Pages : 77
Book Description
Abstract: Detailed pressure and velocity measurements were acquired at Rec = 20,000 with 3% inlet free stream turbulence intensity to study the effects of position, phase and forcing frequency of vortex generator jets employed on an aft-loaded low-pressure turbine blade in the presence of impinging wakes. The L1A blade has a design Zweifel coefficient of 1.34 and a suction peak at 58% axial chord, making it an aft-loaded pressure distribution. At this Reynolds number, the blade exhibits a non-reattaching separation region beginning at 60% axial chord under steady flow conditions without upstream wakes. Wakes shed by an upstream vane row are simulated with a moving row of cylindrical bars at a flow coefficient of 0.91. Impinging wakes thin the separation zone and delay separation by triggering transition in the separated shear layer, although the flow does not reattach. Instead, at sufficiently high forcing frequencies, a new time-mean separated shear layer position is established which begins at approximately 72%Cx. Reductions in area-averaged wake total pressure loss of more than 75% were documented. One objective of this study was to compare pulsed flow control using two rows of discrete vortex generator jets (VGJs). The VGJs are located at 59%Cx, approximately the peak Cp location, and at 72%Cx. Effective separation control was achieved at both locations. In both cases, wake total pressure loss decreased 35% from the wake only level and the shape of the Cp distribution indicates that the cascade recovers its high Reynolds number (attached flow) performance. The most effective separation control was achieved when actuating at 59%Cx where the VGJ disturbance dominates the dynamics of the separated shear layer, with the wake disturbance assuming a secondary role only. On the other hand, when actuating at 72%Cx, the efficacy of VGJ actuation is derived from the relative mean shear layer position and jet penetration. When the pulsed jet actuation (25% duty cycle) was initiated at the 72%Cx location, synchronization with the wake passing frequency (8.7Hz) was critical to produce the most effective separation control. A 20% improvement in effectiveness over the wake-only level was obtained by aligning the jet actuation between wake events. A range of blowing ratios was investigated at both locations to maximize separation reduction with minimal mass flow. The optimal control parameter set for VGJ actuation at 72%Cx does not represent a reduction in required mass flow compared to the optimal parameter set for actuation at 59%Cx. Differences in the fundamental physics of the jet interaction with the separated shear layer are discussed and implications for the application of flow control in a full engine demonstrator are reviewed. Evidence suggests that flow control using VGJs will be effective in the highly unsteady LPT environment of an operating gas turbine, provided the VGJ location and amplitude are adapted for the specific blade profile.
Low Reynolds Number
Author: Mustafa Serdar GençPublisher: BoD – Books on Demand
ISBN: 9535104926
Category : Science
Languages : en
Pages : 176
Book Description
This book reports the latest development and trends in the low Re number aerodynamics, transition from laminar to turbulence, unsteady low Reynolds number flows, experimental studies, numerical transition modelling, control of low Re number flows, and MAV wing aerodynamics. The contributors to each chapter are fluid mechanics and aerodynamics scientists and engineers with strong expertise in their respective fields. As a whole, the studies presented here reveal important new directions toward the realization of applications of MAV and wind turbine blades.